Influence of Tool Rotational Speed on Microstructure, Mechanical Properties and Corrosion Behaviour of Friction Stir Welded Aa 7068-T6 Aluminium Alloy

In this study, AA 7068-T6 plates of 6 mm thickness were friction stir welded in butt configuration at tool rotational speeds of 800 rpm, 1100 rpm and 1400 rpm. The welding speed and the axial force were held constant at 45 mm/min and 7 kN respectively keeping the tool tilt angle at zero degrees. Microstructures at different weld zones were examined. Hardness, tensile and corrosion tests were conducted. It was observed that keeping the other factors constant, an increase in the tool rotational speed reduces weld hardness, Ultimate tensile strength (UTS) and corrosion resistance. The weld produced at 800 rpm, 45 mm/min and 7 kN have shown the highest UTS of 410 MPa and average hardness of 152 HV whereas joints prepared at 1400 rpm exhibited the lowest UTS of 289 MPa and average hardness of 145HV. The base metal exhibited good corrosion resistance than the welded joints. A decreasing trend in corrosion resistance was observed for the welded joints with an increase in the rotational speed